The first Korean EGS project started in December 2010 in Pohang aiming to achieve 1 MW scale power generation in a doublet system.
The site is located in the Heunghae Basin covered by Tertiary sedimentary rocks and quaternary alluvium. Underneath the sedimentary rocks lay a sequence of andesites and crystal tuffs, and the Paleozoic granodiorite basement below 2.4 km. The temperature was >140° at 4.2 km measured three days after drilling.
There are two deep boreholes; PX-2 with a measured depth (MD) of 4’348 m and PX-1 of 4’362 m MD. The distance between the two deep borehole is 6 m, and around 600 m at the surface and in the reservoir, respectively. Four medium depth boreholes (BH-1 to BH-4) with the maximum depth of 2.4 km and one exploration borehole (EXP-1) exist nearby.
Five hydraulic stimulations were conducted with a total injected volume of < 13’000 m3 (net volume < 6’000 m3) from January 2016 to September 2017. Two months after the fifth hydraulic stimulation, the Mw 5.5 Pohang earthquake occurred on 15 November 2017. After a yearlong study, the government-appointed commission concluded that the Mw 5.5 earthquake had been triggered by the hydraulic stimulations. Numerous studies are currently being conducted in search of causal linkage, triggering mechanism, refined seismic analysis and lessons learnt from this highly unprecedented event and the EGS project.
The Pohang EGS project was suspended right after the Mw 5.5 earthquake 2017 and officially terminated in April 2019. Currently no geothermal operation is going on at the site.